The study of a series of biologically related alkylating agents was continued. Investigations included 1H, 13C and 17O nuclear magnetic resonance spectroscopic, as well as X-ray structural studies of carbocationic, as well as oxonium and carboxonium ion type systems. Novel chloromethylhalonium ion type alkylating agents were prepared and studied, including their formation mechanism. The protonation, as well as related radical-cation and dication formations of polycyclic aromatic hydrocarbons was also studied. Electrophilic hydroxylation and epoxidation reactions of hydrocarbons was carried out under stable ion conditions. The study of the formation of nitrosamines was continued. Unexpectedly, it was discovered that nitronium ion reactions (i.e. nitrate precursors) can also give nitrosamines. The mechanism and implications of this interesting finding was explored.